Question

Prepare potash alum and submit it for inspecation

Answer 1

Answer:

What is Potash alum?

Potash alum is also called potassium aluminium sulfate is a chemical compound commonly encountered as the dodecahydrate. It is a double salt widely used in medicine and in the water purification process. Potash alum is not a complex salt. The chemical formula of potash alum is K2SO4.Al2(SO4)3.24H2O.

Aim:

To prepare potash alum from potassium sulfate and aluminium sulfate through crystallization.

Theory:

The formula for potash alum is K2SO4.Al2(SO4)3.24H2O. It is prepared by crystallizing the alum from a concentrated solution containing equimolar amounts of potassium sulfate and aluminium sulfate. It is a colourless, crystalline solid with a sour taste. The crystal of potash alum is octahedral in shape. It is commonly known as ‘fitkari’.

The chemical reaction is given below.

K2SO4(aq) + Al2(SO4)3(aq) → K2SO4.Al2(SO4)3.24H2O(s) (Potash Alum)

While dissolving aluminium sulphate in warm water a little amount of dilute sulfuric acid is added in order to prevent the hydrolysis of this salt.  

When a solution containing two inorganic salts in a definite proportion is allowed to crystallize a double slat is said to have separated. The name alum is given to the special series of double salts. Aluminium is the most abundant metal and the recycling of aluminium products by melting and recasting into other metal products are used in the production of various aluminium compounds. In that one of the most useful compounds is potash alum.

1. Materials Required:
2. Potassium sulphate
3. Aluminium sulphate
4. Dil. sulfuric acid
5. Distilled water
6. Beaker
7. Conical flask
8. Tripod stand
9. Funnel
10. Burner
11. China dish
12. Wire gauze
13. Filter paper

Procedure:

1. Weigh 12.5g of potassium sulfate and dissolved in a minimum quantity of distilled water in a beaker. Stir to dissolve the crystals.
2. Take a conical flask, in that dissolve 50g of aluminium sulfate in warm water and add 3ml of dilute sulfuric acid to make the solution clear.
3. Filter the solutions if it is not clear.
4. Mix the two clear solutions in a china dish.
5. Place the china dish on a wire gauze over a burner.
6. Stir the solution and concentrate the solution till the crystallization point is reached.
7. Place the solution over a beaker containing cold water for a few hours.
8. Crystals of potash alum will get separated, filter then from the mother liquor and wash them with a small quantity of cold water.
9. Dry the crystals by pressing gently between the folds of the filter paper.
10. Weigh them on the chemical balance to know the yield.